X-Ray structural studies of stereoisomeric bi(14H-dibenzo[4,5:6,7][1,3]diazepino[2,1-a]isoindol-14-ylidene)s obtained from the reaction of 2,2′-diaminobiphenyl with o-phthalaldehyde

Abstract

Reaction of 2,2′-diaminobiphenyl with o-phthalaldehyde yielded a number of products including two bi-(14H-dibenzo[4,5:6,7][1,3]diazepino[2,1-a]isoindol-14-ylidene)s, (A) and (B); each was converted on heating into a third isomer (D). The crystal structure of (A), and that of (D), as the solvated trifluoroacetate salt, were determined; (A), previously thought to be the trans-isomer, is in fact the cis-(R,R)/(S,S)-isomer (1a), a racemic compound, and (D) is the meso trans-(R,S)isomer (2b). Compound (B) is considered to be the racemic trans-(R,R)/(S,S)-isomer (2a). The crystal structures of (A) and (D) and the ¹³C n.m.r. and u.v. spectra of all three isomers are discussed.